Modelling of future flood risk across Canada under climate change
Climate change has induced changes in key climate variables and hydrological cycle in Canada. In this study, future runoff projections made by 21 GCMs following four Representative Concentration Pathways (RCPs) are used as inputs into a macro-scaled hydrodynamic model: CaMa-Flood to simulate 25 km resolution daily streamflow across Canada for historical (1961-2005) and future (2061-2100) time-periods. Future changes in flood-hazard as a consequence of changes in flooding frequencies of historical 100-year and 250-year return period flood events, and changes in the month of occurrence of extreme flows are analyzed. Changes in flood risk at Canada’s 100 most populous cities and 1072 regulated flow gauging stations are also estimated. Assessment results indicate that most of northern Canada, southern Ontario, southern British Columbia, northern Alberta, Manitoba and Saskatchewan are projected with future increases in flooding frequencies. Updated return periods of historical 100-year floods are projected to be in the range of 10-60 years by the end of 21st century in these regions. Among the cities analyzed, Sault Sainte Marie (RCP 2.6), Saint Catharines-Niagara (RCP 4.5), and Halifax (RCP 6.0), and Sault Sainte Marie (RCP 2.6) are projected with largest increases in flood hazard, with an updated historical return periods of 4-year, 4-year, 1-year, and 4-year respectively. Highly populated cities like Toronto (RCP 2.6 and RCP 8.5), and Montreal (RCP 4.5 and RCP 6.0) are projected with most increases in flood-risk whereas Kelowna (RCP 2.6, RCP 4.5), Hamilton (RCP 6.0), and Trois-rivieres (RCP 8.5) are projected with most decreases in flood-risk in future. Among the regulated flow gauging stations, Reindeer River Above Devil Rapids in Saskatchewan (RCP 2.6 and 6.0), Playgreen Lake at Entrance to East Nelson River in Manitoba (RCP 4.5), and St. Marys River at Sault Ste. Marie in Ontario (RCP 8.5) are projected with most increases in flood hazard where the return period of historical 100-year floods are expected to become 2-year return period flooding event by the end of 21st century. Similar observations are also made in case of 250-year return period flood events.
Climate change, Flood frequency, Flood risk, Return period, Uncertainty
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